The present invention is generally related to providing protection for various products such as foods, drugs, chemicals and other products, including dry, semi-moist and liquid products as well as products which contain particulate of varying sizes and shapes.
The methods used to package and protect foods, drugs and chemicals today include cans, bottles, jars, laminated canisters, and pouches as well as semi-rigid plastic containers. Additionally, most food, beverage and pharmaceutical products require more product protection that can be achieved by a single polymeric material. It is known that different combinations of materials can be used together to achieve desired protection in the areas of gas, moisture, chemical and thermal resistance properties, as well as physical properties that cannot be achieved economically by other means. In some instances, the desired properties can be achieved by a physical blend of various materials, such as Dupont Sclair™ films which are an alloy or blend of nylon and polyethylene used in the packaging of fluid milk and other food products. Recently, inorganic nano sized particles have been found to make significant improvements in the gas barrier properties of most polymers in which they are dispensed (see, e.g., JP 89308879.9). By themselves, these alloys have been useful in providing some additional shelf life for refrigerated products or for products that are fairly tolerant of oxygen.
In some instances, nano particles have been used in conjunction with oxygen scavengers to improve the gas barrier of the carrier polymer and provide a source of moisture for an anti-oxidant of the oxygen scavenger that make up the alloy (see, e.g., JP 63281964). These blends, which contain both an oxygen scavenger and inorganic platelets to create a tortuous path, are an improvement but do not, by themselves, provide the cost nor esthetics and continuing protection required for extended shelf life or shelf image of most oxygen intolerant, shelf stable foods and other products.
For critical packaging requirements of this type, the solution had been to package products in metal cans or glass jars. This solution endured until the development of semi-rigid, multi-layer, high-barrier plastics, which were commercialized in the mid 1980's in packaging for such products as puddings, fruit compotes and single serve entrees. Previously, multi-layer, adhesive laminated, high-barrier thermoformed sheet technology had been used for small containers to package jams and jellies for single-serve, ready to use packs. These packs were produced based upon aqueous coating technology utilizing Poly-Vinylidene Chloride (PVDC). The PVDC coating, while very effective in a flat film form, is not capable of being stretched more that 10% without breaking apart. This prevents aqueous PVDC coatings from being used for larger sized or deeper packages. To overcome extensibility problems, further development resulted in an extrudable version and a method of combining it in a laminar method through a process known as coextrusion, as disclosed in U.S. Pat. No. 3,557,265.
Coextrusion was used in the creation of packages for both high and low acid foods, with the first publicized application of “plastic cans” being thermally processed (retorted) in the mid-1970's. “Plastic cans” are prevalent today, and are typically produced using a process known as solid-phase pressure-forming and, more recently, using multi-layered injection blow molding and/or extrusion blow molding processes. This process was developed in the early 1970's in an effort to create sales opportunities for a newly commercialized plastic polymer known as polypropylene. Johnson U.S. Pat. No. 3,546,746 teaches that plastic articles can be thermoformed not only from flat sheets but also from pre-cut shapes called billets or blanks. U.S. Pat. No. 3,502,310 to Coffman demonstrates an improved process involving heating the billets continuously and forming several articles simultaneously.
The primary advantage of forming articles and specifically containers from pre-formed plastic billets did not become obvious until the mid 1980's when multi-layered plastic sheeting began to be used for the packaging and preserving of processed shelf stable foods. Plastic barrier containers have now become common and the primary methods of producing containers for shelf-stable applications are described below.
In a representative process, adhesively laminated or coextruded sheet is web or sheet fed through a radiant or contact heating oven and then thermoformed into its final shape by means of vacuum and/or pressure, with an additional assist from a movable plug to help distribute material for deep or tall containers, where required. Containers are then trimmed out of the web or sheet by trim tooling, which can either be a trim in place style which removes the part from the web as part of the forming process, or an off-line style in which parts can be trimmed out of the web or sheet in a secondary trimming process. Web scrap generated in this process typically exceeds 40% of the total web used in the process, and is not uncommon to see scrap losses of 50% on round container shapes. This high percentage of scrap increases the cost of the finished parts, since not all of the scrap can be recovered. In addition, the recoverable portion of the scrap is valued only at the cost of the lowest priced material in the web, since the only real value of such material is as a structural component. The benefit of the more expensive barrier materials is lost when the web skeleton is ground up to make regrind.
To maintain the barrier characteristics of the original individual layers or phases of the laminated sheet, each individual material must maintain its individual integrity. Grinding the web skeleton into regrind destroys the integrity of the individual layers. The resulting blended materials, when extruded into a sheet, have none of the gas barrier characteristics of the original multilayered sheet and in fact will have lost some of the physical properties of the initial structural material used in the original sheet manufacture. Additionally, some of the components in the original multilayered sheet are typically approved for indirect food contact only in high temperature food processing conditions. Because these materials are no longer sandwiched into the center portion of the sheet, it becomes necessary to place a separate food contact layer between the regrind component and the food product to insure that the materials, which are only acceptable for indirect food contact, are kept in that position.
In addition, if the initial multilayered sheet was clear, the use of regrind will diminish the clarity in direct proportion to the amount of regrind being used in the sheet. For containers which contain both polypropylene and EVOH (EVOH @ 1.5% or more), it has been commercially demonstrated that structures which incorporate web scrap of 15% or more are noticeably cloudy and at levels of 20% become unacceptable for most applications. The web skeleton that is not recovered and reused back into the manufacture of sheet is then sold off as waste, with a salvage value less than half that of the reused regrind, further increasing the cost of the original parts produced from the web.
Reduced scrap thermoforming has been developed to a commercial state in the U.S. by two patented methods, the first being a scrapless forming process as shown in U.S. Pat. No. 3,947,204, and the second being a billet forming process as shown in U.S. Pat. Nos. 3,502,310; 3,546,746; and 3,538,997. Both methods incorporate process benefits described by Briston, et al., in PLASTICS IN CONTACT WITH FOODS, 466 pages, received in the PTO scientific library Dec. 31, 1974, as well as the process improvements for transporting the billets identified in Frados et al., PLASTICS ENGINEERING HANDBOOK, ISBN 0-442-22469-9, Library of Congress Catalog Card Number 75-26508 pages 315 & 316, describing the Hoffco/Beloit Forming System. The original forming processes also benefited from the teachings of U.S. Pat. No. 3,538,997, which discloses the individual transportation of the billets through the oven and into the forming station wherein the carrier becomes a central part of the forming tool. Once formed, the carrier tray transports the finished parts to the removal station and begins the cycle again. This process is adapted in Parkinson U.S. Pat. No. 4,836,764.
Plastic containers used in the packaging of shelf stable foods required not only adequate barrier to prevent the oxidation of the products contained within the package, but also had to prevent the gain or loss of moisture as well. As discussed, it is possible to design a multilayered package with the required barrier properties. However, the closures for these types of packages require a different approach or method so as to allow easy access to the product. Initially, metallic foils laminated and/or extrusion coated with polymeric thermal sealing compounds were developed to provide controllable seal strengths for ease of opening. In order to utilize these flexible-sealing membranes, a sealing surface or flange had to be designed into the package. These sealing surfaces typically were flat, although some exceptions were found to be workable such as that created by Embro and disclosed in U.S. Pat. No. 4,282,699.
Metal can ends have also been used to seal these newer plastic containers with some success. However the can ends require that the plastic container have a flange, which is approximately 0.021″ thick. However, the starting thickness of the sheet is typically greater that 0.080″ and can be as thick as 0.115″. The required thickness of the plastic container flanges thus necessitates that the sheet be significantly reduced in thickness in order to meet the specifications of the metal end. Reducing the sheet thickness to this degree typically creates interlayer adhesion and other problems. Interlayer adhesion of the compression molded double seamable flange can cause operational problems if the problems are not caught before they appear on the production floor. Additionally, the cut edge exposes the hydroscopic barrier materials to a high level of moisture pickup, thereby diminishing its barrier properties.
It is an object of the present invention to provide a product package that overcomes the above-noted problems with prior art packages. It is a further object of the invention to provide a multi-component product package that can be formed in various shapes and sizes, and is not limited to use of round mating surfaces as in the prior art. Another object of the invention is to provide a product package providing a seal of high integrity between the body and the end members of the package. A still further object of the invention is to provide a product package that can be efficiently manufactured with minimal waste using a container body closed by a pair of end members. Another object of the invention is to provide a product package that has the same relative or improved amount of product protection as prior art packages, while consuming much less energy in the comparative total life cycle. A still further object of the invention is to provide a product package in which the container body can be contoured according to manufacturer or user requirements. Yet another object of the invention is to provide a product package having a reclosable opening to provide access to the contents of the package, and which provides convenience in opening, dispensing and re-closing the package. A further object of the invention is to provide a product package that is capable of efficient and rapid mass production, to provide a lower cost package than is currently available for barrier property containers. A still further object of the invention is to provide a product package that is relatively inexpensive to manufacture, yet which provides improved barrier characteristics and flexibility in package design over prior art packages.